Cooling system frozen in the morning on 2004 Kia Sedona

I live in a very cold climate and for last few days my antifreeze has been freezing therefore the van is overheating. In the fall we by-passed the lines going back to rear heater core as there was leak and the lines were corroded. We were on vacation at the time so it had to be a quick fix that did not get correctly fixed before winter. It seems that once the anti freeze gets warm and starts to circulate the temperature drops back to normal and I start getting heat inside. Do you have any suggestions on what is happening and how to fix it?

never start your heater fan till the temperature has risen ( it acts like a freezer plant ) batterys with low charge can freeze up if road speed too fast I keep tractors and vehicles starting at 45 degrees below { f ) wind goes really cold down to 65so you should not have problem we run our antifreeze no less than 50/50 It sounds like your problem is circulation at the start so anything you can do to get it warm will help put hotter thermostat in cover with blanket till temp risesif you use cardboard in front of rad make sure you have 1/4 circle cut out in center to allow rad to circulate. If on a farm - park on manure pile will keep it warmer Put in-line water heater GOOD LUCK